(CNN) —  

The House Energy and Commerce Committee says Health and Human Services Secretary Alex Azar has declined a request to appear before the committee to discuss family separations at the US southern border.

Chairman Frank Pallone, a New Jersey Democrat, personally requested that Azar testify before the committee, but the secretary’s office declined the request on Tuesday, according to the committee spokesman.

“One way or another,” Azar will have to testify before the Energy and Commerce Committee, Pallone said in a statement. He called Azar’s denial of the request to testify “unacceptable” and said it is “outrageous” that Azar has yet to appear before Congress for a hearing on the controversial policy.

Between April 19 and May 31 last year more than 2,600 children were separated from their parents at the southern border, after the Trump administration ordered federal prosecutors to pursue criminal charges against all migrants who crossed the border unlawfully. The controversial policy was ultimately reversed in June with an executive order.

A new inspector general report released on Thursday found that “thousands” more children had been separated than previously reported by the government.

The new report “raises new questions of whether this Administration was engaging in such tactics earlier than it reported,” according to Pallone’s statement.

Azar’s office did not dispute that he had declined the invitation to testify. His office contended in a statement to CNN that the secretary and Pallone have “spoken directly.” According to the statement, Azar “understands and appreciates the important role of congressional oversight and is committed to providing necessary information and expertise.”

The statement says Health and Human Services staff have “communicated in good faith” with the congressional staff “to provide the department’s most knowledgeable subject matter experts to the subcommittee.”

“HHS has also facilitated numerous briefings with congressional staff to provide updates” on the Unaccompanied Alien Children program and the work of the Office of Refugee Resettlement, “including a weekly call with the Hill – and has coordinated over 100 visits for members of Congress and more than 50 members of the media to ORR-funded facilities,” according to the statement by Azar’s office.

The House Energy and Commerce Committee’s Subcommittee on Oversight and Investigations sent a letter on Friday to Azar requesting that he turn over documents related to the administration’s “zero-tolerance” immigration policy.

The letter came less than a day after Sen. Jeff Merkley, an Oregon Democrat, released a 2017 draft memo that details plans to separate families months before the “zero-tolerance” policy was announced by the administration.

CNN’s Priscilla Alvarez and Geneva Sands contributed to this report.